Summit is a city in Union County, New Jersey, United States. At the 2010 United States Census, the city's population was 21,457, reflecting an increase of 326 from the 21,131 counted in the 2000 Census, which had in turn increased by 1,374 from the 19,757 counted in the 1990 Census. Summit had the 16th-highest per capita income in the state as of the 2000 Census.Originally incorporated as Summit Township by an act of the New Jersey Legislature on March 23, 1869, from portions of New Providence Township and Springfield Township, Summit was reincorporated as a city on March 8, 1899.Possible derivations of Summit's name include its location atop the Second Watchung Mountain; the Summit Lodge, the house to which jurist James Kent moved in 1837 and which stands today at 50 Kent Place Boulevard; and to a local sawmill owner who granted passage to the Morris and Essex Railroad for a route to "the summit of the Short Hills".